Question 1

Which JSON library does it target, Newtonsoft or System.Text.Json?

Accepted Answer

Both are common. The tool emits `[JsonPropertyName("snake_case_key")]` (System.Text.Json, .NET 5+) by default since it's the modern default. For Newtonsoft, switch the attribute to `[JsonProperty("snake_case_key")]`, same semantics, different namespace (`Newtonsoft.Json`). The class shape is identical either way.

Question 2

How are property names converted?

Accepted Answer

JSON `snake_case` and `camelCase` keys become C# `PascalCase` properties (the .NET convention). The original JSON key is preserved via attribute so deserialization still works: `user_id` in JSON ↔ `UserId` in C#. Acronyms (`url`, `id`, `api`) become `Url`, `Id`, `Api` (Microsoft's recommended style, not all-uppercase).

Question 3

How are nullable fields handled?

Accepted Answer

From a single sample, the tool can't tell what's nullable. By default, value types (int, bool, DateTime) become non-nullable; reference types (string, List) become nullable. For nullable value types, add `?` manually: `public int? Age { get; set; }`. With nullable reference types enabled (`enable` in csproj), string fields become `string?` when needed.

Question 4

What about dates and GUIDs?

Accepted Answer

Strings matching ISO 8601 (`2024-03-12T10:30:00Z`) are inferred as `DateTime`. Strings matching the GUID pattern (`8-4-4-4-12` hex) become `Guid`. Other date formats (Unix epoch as int, custom formats) need manual `[JsonConverter]` attributes. For nullable dates, use `DateTime?` and let the deserializer handle null → null.

Question 5

Are nested objects flattened or separate classes?

Accepted Answer

Separate classes, one per distinct nested shape. `{user: {address: {city: ...}}}` generates `RootObject` → `User` → `Address`. Class names come from property names (Address, User). For arrays of objects, the item class is also separate (Order → OrderItem). Reuse: if two nested objects have the same shape and name, the tool emits one class.

Question 6

How do I integrate the generated classes?

Accepted Answer

Drop the .cs file into your project, add `using System.Text.Json;`, and deserialize: `var data = JsonSerializer.Deserialize<RootObject>(jsonString, options);` where options enables `PropertyNameCaseInsensitive` if your JSON has mixed-case keys. For ASP.NET Core minimal APIs, the framework auto-binds JSON requests to the model class, no manual deserialization.

Question 7

What about record types or init-only setters?

Accepted Answer

The tool emits classes with `{ get; set; }` properties by default, the most-compatible style. For C# 9+ records, manually convert: `public record User(int Id, string Name);`. For init-only setters (immutable after construction): `public string Name { get; init; }`. Records work better with System.Text.Json source generators.

Question 8

Is my JSON sent anywhere?

Accepted Answer

No. Type inference and C# emission are pure JavaScript in your browser. Your sample JSON, potentially production data, secret API responses, internal schemas, stays local. No network requests during conversion.

Question 9

What standards does JSON to C# Class validate against?

Accepted Answer

JSON to C# Class checks compliance with RFC 8259 (JSON), C# language specification.

Question 10

What are the limitations of JSON to C# Class?

Accepted Answer

Generated classes use System.Text.Json attributes by default Does not handle polymorphic JSON schemas Nullable reference types depend on C# version

JSON Type	C# Type	Generic Wrapper	Attribute Logic
Integer	`int` / `long`	-	Range detection
Float	`double` / `decimal`	-	Precision mapping
String	`string`	-	Standard mapping
ISO 8601	`DateTime`	-	Auto-parsing support
Array	`List<T>`	`T[]`	Homogeneous inference
Null	`T?`	Nullable Value Types	Conditional mapping

JSON to C# Class

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What is JSON to C# Class?

Frequently Asked Questions

Technical Deep Dive

JSON to C# Class

Two-Way Conversion

Type-Faithful

Production-Sized

01 Type Inference Matrix

02 Generation Pipeline

Runs 100% in your browser

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